Effects of long-term storage on Mal d 1 content of four apple cultivars with initial low Mal d 1 content.

BACKGROUND: Up to 6.6% of adults and 11.5% of children aged between 0 and 6 years are reporting a perceived fruit allergy. In the last group 8.5% perceived reactions against apple. To keep allergic reactions as low as possible and to make apple consumption more tolerable for patients allergic to apple, the Mal d 1 content of four apple cultivars ('Boskoop', 'Elise', 'Pinova', 'Santana' and 'Topaz') were analyzed, to identify apple cultivars with only a low Mal d 1 content. Further, the development of Mal d 1 content of low-allergenic cultivars should be investigated during long-term storage. RESULTS: The lowest Mal d 1 content was measured for fruits of the cultivar 'Santana' at harvest, followed by 'Pinova' and 'Elise' after storage without 1-MCP. Nearly all fruits treated with 1-MCP had a significantly lower Mal d 1 content than fruits without 1-MCP, except for 'Boskoop' fruits after 44 weeks of storage. Apple cultivars with a low Mal d 1 content are not a cross of 'Golden Delicious' with another cultivar, with the exception of 'Pinova' which is a cultivar from the so-called 'Pi-series', which have a moderate resistance to scab and mildew. First experiments on tomatoes and peanuts have shown a reduction of allergic proteins in older and child generations after transfer of RNA. This reduction is probably based on an alteration of gene expression regulating the synthesis of allergic proteins, leading to changes in protein composition in the fruit. CONCLUSION: Individuals allergic to apple should choose the described cultivars with relative low Mal d 1 content. If breeders want to breed cultivars with low allergy, they should avoid crossings with 'Golden Delicious'.

The impact of catechin and epicatechin, total phenols and PPO activity on the Mal d 1 content in apple fruit.

The most important apple allergen in Central Europe and North America is Mal d 1. Apples are a very important source of secondary plant metabolites like polyphenols in human nutrition. It is known that oxidised phenols can bind proteins. These irreversible bindings can lead to a reduced allergenicity. The most important phenols in apple are epicatechin, catechin and their polymeric structures, which have been identified as substrates of the polyphenoloxidase (PPO). The aim of this study was to analyse the influence of naturally occurring catechin and epicatechin contents in apple on the allergenicity of apple fruits. Fruits of the cultivars 'Elstar', 'Diwa' and 'Boskoop' were harvested and stored for 8 and 12 weeks in a cold-chamber at 2 °C. Mal d 1-, catechin-, epicatechin- and total phenol content as well as the activity of PPO were determined. Correlation analysis showed that naturally occurring catechin as well as epicatechin has no impact on the Mal d 1 content of the tested cultivars: correlation coefficient ranged from -0.203 to 0.501 for the correlation between Mal d 1 and catechin. The results further indicated that the activity of PPO is more important than the content of total phenols to reduce the Mal d 1 level. If there is a high PPO activity, Mal d 1 could be reduced even if the total phenol concentration is low.